Timing the impact of literacy on visual processing

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 111; no. 49; pp. E5233 - E5242
• Main Authors: Pegado, Felipe, Comerlato, Enio, Ventura, Fabricio, Jobert, Antoinette, Nakamura, Kimihiro, Buiatti, Marco, Ventura, Paulo, Dehaene-Lambertz, Ghislaine, Kolinsky, Régine, Morais, José, Braga, Lucia W., Cohen, Laurent, Dehaene, Stanislas
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 09.12.2014; National Acad Sciences
• Series: PNAS Plus
• Subjects: Adult; adulthood; adults; Aged; Behavior; Biological Sciences; brain; Brain - pathology; Brain Mapping; childhood; Cognition & reasoning; Cognitive science; Education; Educational Status; Electrophysiology; Evoked Potentials; Female; Humans; Image Processing, Computer-Assisted; Impact analysis; Learning; Literacy; Magnetic Resonance Imaging - methods; Male; Middle Aged; Neuronal Plasticity; NMR; Nuclear magnetic resonance; Photic Stimulation; PNAS Plus; Reading; Regression Analysis; Social Sciences; Software; Temporal Lobe - pathology; Time Factors; Visual Perception; Visual task performance; Visualization; reading; brain plasticity; education
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1417347111

Learning to read requires the acquisition of an efficient visual procedure for quickly recognizing fine print. Thus, reading practice could induce a perceptual learning effect in early vision. Using functional magnetic resonance imaging (fMRI) in literate and illiterate adults, we previously demonstrated an impact of reading acquisition on both high- and low-level occipitotemporal visual areas, but could not resolve the time course of these effects. To clarify whether literacy affects early vs. late stages of visual processing, we measured event-related potentials to various categories of visual stimuli in healthy adults with variable levels of literacy, including completely illiterate subjects, early-schooled literate subjects, and subjects who learned to read in adulthood (ex-illiterates). The stimuli included written letter strings forming pseudowords, on which literacy is expected to have a major impact, as well as faces, houses, tools, checkerboards, and false fonts. To evaluate the precision with which these stimuli were encoded, we studied repetition effects by presenting the stimuli in pairs composed of repeated, mirrored, or unrelated pictures from the same category. The results indicate that reading ability is correlated with a broad enhancement of early visual processing, including increased repetition suppression, suggesting better exemplar discrimination, and increased mirror discrimination, as early as ∼100–150 ms in the left occipitotemporal region. These effects were found with letter strings and false fonts, but also were partially generalized to other visual categories. Thus, learning to read affects the magnitude, precision, and invariance of early visual processing. Significance How does learning to read affect visual processing? We addressed this issue by scanning adults who could not attend school during childhood and either remained illiterate or acquired partial literacy during adulthood (ex-illiterates). By recording event-related brain responses, we obtained a high-temporal resolution description of how illiterate and literate adults differ in terms of early visual responses. The results show that learning to read dramatically enhances the magnitude, precision, and invariance of early visual coding, within 200 ms of stimulus onset, and also enhances later neural activity. Literacy effects were found not only for the expected category of expertise (letter strings), but also extended to other visual stimuli, confirming the benefits of literacy on early visual processing.